The Mississippi Supreme Court on Thursday threw out the murder conviction of Curtis Flowers, a black man who has been tried six times for the same crimes, two months after the United States Supreme Court ruled that the prosecutor, who is white, unconstitutionally kept black people off the jury.

Mr. Flowers, 49, has been accused of murder in the 1996 killings of four people in a furniture store in Winona, Miss. All six prosecutions have either ended in mistrial or convictions that were reversed on appeal.

The case sparked a national conversation about race in the criminal justice system after a podcast investigated the decades-long effort by the prosecutor, Doug Evans, to convict Mr. Flowers.

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Prosecutor Doug Evans, center, at the 2010 murder trial for Curtis Flowers. Clemmie Flemming, right, pointed out where she said she saw Mr. Flowers on the morning of the killings.CreditTaylor Kuykendall/Commonwealth, via Associated Press

Thursday’s move by the Mississippi Supreme Court was expected after the United States Supreme Court said in June that Mr. Evans had violated the Constitution in Mr. Flowers’s sixth trial by striking black jurors. In the six trials for Mr. Flowers, 61 of the 72 jurors were white.

Reporters at APM Reports, a division at American Public Media, highlighted Mr. Flowers’s case last year in the podcast “In the Dark.”

Reporters with the podcast poked holes in the forensic evidence prosecutors used and raised questions about an informant who said Mr. Flowers had confessed to him. In February, the podcast won a George Polk award, a prestigious journalism prize, for its work about the case.

The United States Supreme Court noted in June that Mr. Flowers’s first two convictions were reversed based on prosecutorial misconduct. His third conviction was reversed after the Mississippi Supreme Court said Mr. Evans had discriminated against black jurors during jury selection.

The fourth trial ended in a mistrial. In the four trials, held between 1997 and 2007, Mr. Evans used all 36 of his peremptory challenges to strike black potential jurors.

“The state’s actions in the first four trials necessarily inform our assessment of the state’s intent going into Flowers’s sixth trial,” Justice Brett M. Kavanaugh wrote in the majority opinion. “We cannot ignore that history.”

The fifth trial also ended in a mistrial because of a hung jury. The jury at the sixth trial, made up of one black and 11 white jurors, convicted Mr. Flowers in 2010 and sentenced him to death. The Mississippi Supreme Court had affirmed the conviction and sentence.

But Justice Kavanaugh said that Mr. Evans had violated the Constitution.

The United States Supreme Court noted that during jury selection, Mr. Evans asked black prospective jurors an average of 29 questions each, while asking the 11 white jurors who were eventually seated an average of one question each.

“Equal justice under law requires a criminal trial free of racial discrimination in the jury selection process,” Justice Kavanaugh wrote.

Mr. Evans said he excluded black potential jurors for a variety of reasons, including that they knew witnesses or members of Mr. Flowers’s family, had qualms about the death penalty or had turned up late for jury selection.